Wireless Strain Sensors, Detection Methods, and Systems

ABSTRACT

A strain sensor comprises a transmitting element; a receiving element wirelessly coupled to the transmitting element; and a modulating element located on a rotating component, wherein the modulating element modulates the wireless coupling between the transmitting element and the receiving element, wherein the modulation of the wireless coupling is indicative of strain on the rotating component. A method of detecting strain in a rotating component of a rotary machine comprises wirelessly coupling a transmitting element and a receiving element; modulating the coupling with a modulating element located on the rotating component; and calculating the strain in the rotating component based on the modulation of the coupling.

BACKGROUND OF THE INVENTION

The present disclosure generally relates to measurement of strain inrotating machinery.

Rotary machinery, for example, blades in an aircraft engine, mayexperience strain during operation, which may damage the machinery.Accurate measurement of strain is necessary to take appropriate measuresto correct or prevent any damage that may occur in the rotary machinery.One approach to measurement of strain in rotary machinery may use wiredstrain sensors, which require wiring between a rotating component and astationary part of the rotary machinery. However, a wired approach maybe complex, expensive, and unreliable, due in part to the hightemperature of the machinery in operation, as the electroniccharacteristics of the wiring may limit the range of temperatures overwhich a wired strain sensor may operate accurately.

Due to the limitations of wired strain sensors, wired strainmeasurements of a rotary machine may only be taken during testing of therotary machinery; during operation in the field, wires strain sensorsmay be impractical. However, monitoring strain over the entire lifespanof the rotary machinery is desirable to ensure reliable operation of therotary machinery. Strain measurements taken in the field may becorrelated with control parameters to optimize field operation of therotary machinery. Change observed in strain measurements over time maybe also used to assess the health of the blades of the rotary machinery,allowing for appropriate maintenance scheduling.

Accordingly, there remains a need in the art for a strain sensor that isaccurate over a wide range of temperatures and conditions, and that maybe used over the lifespan of rotary machinery.

BRIEF DESCRIPTION OF THE INVENTION

Disclosed herein are systems and methods for a wireless strain sensor.In one embodiment, a strain sensor comprises a transmitting element; areceiving element wirelessly coupled to the transmitting element; and amodulating element located on a rotating component, wherein themodulating element modulates the wireless coupling between thetransmitting element and the receiving element, wherein the modulationof the wireless coupling is indicative of strain on the rotatingcomponent.

A method of detecting strain in a rotating component of a rotary machinecomprises wirelessly coupling a transmitting element and a receivingelement; modulating the coupling with a modulating element located onthe rotating component; and calculating the strain in the rotatingcomponent based on the modulation of the coupling.

This disclosure may be understood more readily by reference to thefollowing detailed description of the various features of the disclosureand the examples included therein.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the figures wherein the like elements are numberedalike:

FIG. 1 shows an example arrangement of a wireless strain sensing system.

FIG. 2 shows an example arrangement of a wireless strain sensor.

FIGS. 3 a and 3 b schematically depict examples of modulating elementpatterns.

FIG. 4 shows an example arrangement of a wireless strain sensor.

FIGS. 5 a, 5 b, and 5 c show example arrangements of modulating elementpatterns.

FIG. 6 shows an example arrangement of a wireless strain sensorcomprising an inductive sensor.

FIG. 7 shows an example arrangement of a wireless strain sensorcomprising a capacitive sensor.

FIG. 8 shows an example arrangement of a wireless strain sensor withauto-referencing.

FIG. 9 shows an example arrangement of a wireless strain sensor withauto-referencing.

FIG. 10 shows an example of a method of detecting strain in a rotatingcomponent of a rotary machine.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows an example arrangement of a wireless strain sensing system.Transmitting element 101 is in wireless communication with receivingelement 102. The connection between transmitting element 101 andreceiving element 102 is modulated by modulating element 103. Modulatingelement 103 may move with respect to transmitting element 101 andreceiving element 102 due to strain in the system. This movement ofmodulating element 103 modulates the wireless coupling betweentransmitting element 101 and receiving element 102, allowing the strainin the system to be determined at receiving element 102.

FIG. 2 shows a cross-section of an engine 200 and illustrates anembodiment of a wireless strain sensor. It should be noted that althoughthe illustrated examples are directed to a turbine engine application,the invention is more broadly applicable to measuring strain in rotatingcomponents of any rotary machine, non-limiting examples of which includewind turbines, and electric motors. Blade 204 rotates about axle 205within stationary component, or shroud, 203. Although only one blade 204is shown in FIG. 2, engine 200 may comprise a plurality of rotatingblades. In the illustrated example, transmitting element 201 andreceiving element 202 are mounted on stationary component 203.Non-limiting examples of a transmitting element 201 may comprise a coil,such as an inductive coil, an antenna structure, metal on an insulator,or a drawn conductor on a ceramic substrate. Non-limiting examples of areceiving element 203 may comprise a coil, such as an inductive coil, anantenna structure, metal on an insulator, or a drawn conductor on aceramic substrate. Transmitting element 201 and receiving element 202are connected by wireless coupling 207. In some embodiments, wirelesscoupling 207 may be a magnetic coupling such as a near field, a mutuallyinductive coupling, or a far field electric field coupling. Forembodiments in which wireless coupling 207 comprises a magneticcoupling, the effective coupling constant (k) of a coupling 207 betweentransmitting element 201 and receiving element 202 is related to therate of change of the magnetic field (B) of wireless coupling 207, i.e.,k˜d/dt(B). As blade 204 rotates, wireless coupling 207 is modulated bymodulating element 206, which is disposed on the surface of blade 204.Strain from the rotation may cause deformation in blade 204 (forexample, blade 204 may stretch), moving modulating element 206 relativeto coupling 107, and causing further modulation of wireless coupling207. Therefore, the modulation of wireless coupling 207 (d(B)/dt) is afunction of the displacement of modulating element 206. In someembodiments, the modulating element 206 may comprise a material thatchanges permeability in response to strain or crystalline deformations,which cause realignment of atomic structure.

Because the strain experienced by blade 204 is a function of thedisplacement of modulating element 206, the strain may be determined asa function of the coupling constant (k) between transmitting element 201and receiving element 202. The strain on blade 204 is thereby wirelesslydetermined using a passive approach with no active electronics or p/njunctions, which may only operate accurately over a limited range oftemperatures. At higher temperatures, leakage through p/n junctions mayincrease to a point where accuracy and life of the electronics areadversely affected. Embodiments of modulating element 206 may comprise ahigh permeability material selected to modulate an inductive circuit, ora relatively high permittivity material selected to modulate thecapacitance of a capacitor circuit. In some embodiments modulatingelement 206 may have a relatively high permittivity with respect to air,allowing for use of a relatively small capacitor. Use of a relativelysmall capacitor allows the strain to be measured more precisely. Themodulating element 206 may be selected to have a high temperature Curiepoint. Embodiments of a wireless strain sensor may produce accurateresults at temperatures up to 1200° F.

FIGS. 3 a and 3 b illustrate exemplary embodiments of modulating elementpatterns. Referring to FIG. 3 a, modulating element 310 a may move inthe direction indicated by the arrows in relation to coupling 302 a,which connects transmitting element 301 and receiving element 302.Referring to FIG. 3 b, modulating element 301 b may move in thedirection indicated by the arrows in relation to coupling 302 b, whichconnects transmitting element 301 and receiving element 302. The amountof displacement of modulating element 301 a or 301 b due to strain onblade 304 may be small; however, a very small displacement of modulatingelement 301 a or 301 b may result in a relatively large modulation incoupling 302 a or 302 b. Coupling 302 a or 302 b may act as anamplifier, allowing strain-based displacement of modulating element 301a or 301 b to be accurately detected.

FIG. 4 shows another example arrangement of a wireless strain sensor400. Receiving element 401 and reader electronics 404 are disposedaround the shroud or approximately at the perimeter area of the blades(not shown). Although the illustrated example is directed to an engine,strain sensor 400 is applicable to any type of rotary machine, includingturbines, motors, or any other non-contact strain sensing application.Transmitting element 402 and sensor components 405 are disposed on oneof the rotating blades. The impedance of the passive circuit formed bytransmitting element 402 and sensor components 405 is modulated by thestrain on the blade in this particular, non-limiting example, as isdiscussed in further detail below regarding FIGS. 5 a, 5 b, and 5 c. Themodulation of the impedance at transmitting element 402 in turnmodulates wireless coupling 403 between receiving element 401 andtransmitting element 402, resulting in a change in impedance atreceiving element 401. The change in impedance at receiving element 402may be used to calculate the strain on the blade by reader electronics404. The strain on the blade may therefore be calculated wirelesslyusing a passive approach with no active electronics or p/n junctions,which may only operate accurately over a limited range of temperatures.Sensor components 405 may be selected to have a high temperature Curiepoint, and hence embodiments of a wireless strain sensor may produceaccurate results at temperatures up to 1200° F.

FIGS. 5 a, 5 b, and 5 c show illustrative embodiments of sensorcomponents 405. Referring to FIG. 5 a, sensor components 505 maycomprise a modulating element 501 a and an inductor 502 a. Strain on theblade moves the relative position of modulating element 501 a withregards to inductor 502 a, as shown by the arrows. Even a small movementof modulating element 501 a in relation to inductor 502 a may induce arelatively large change in the impedance of the circuit formed by sensorcomponents 405 and transmitting element 402, which in turn modulates theresonance frequency and impedance of wireless coupling 403 betweenreceiving element 401 and transmitting element 402, allowing the strainto be wirelessly read out as discussed above with regards to FIG. 4.FIGS. 5 b and 5 c operate in a manner similar to FIG. 5 a, withmodulating element 501 b and 501 c moving relative to inductors 502 band 502 c, respectively. Modulating elements 501 a, 501 b, and 501 c maycomprise a high permeability material in some embodiments.

FIG. 6 shows an alternate embodiment of a wireless strain sensor 600comprising an impedance transformer 606. Wireless strain sensor 600comprises receiving element 601, transmitting element 602, wirelesscoupling 603, and reader electronics 604. The impedance transformer 606shifts the frequency range of operation of the circuit comprised oftransmitting element 602 and sensor components 605 to a more suitablerange, and amplifies the resulting frequency shift detected at receiver601. FIG. 7 illustrates a capacitive embodiment of a wireless strainsensor 700. Wireless strain sensor 700 comprises receiving element 701,transmitting element 702, wireless coupling 703, reader electronics 704,and impedance transformer 706. Sensor components 705 comprise acapacitor in place of the inductor of sensor components 405. In theembodiment shown in FIG. 7, the sensor components 705 may comprise acapacitor and a high permittivity material.

FIG. 8 shows an embodiment of a wireless strain sensor 800 includingauto-referencing. Receiving element 801 and reader electronics 808 aredisposed around the stationary component or approximately at theperimeter area of the rotating components, or, for the example of anengine, the blades (not shown). In the illustrated arrangement,transmitting element 802 and sensor components 806 are mounted on one ofthe blades, as are transmitting element 802 and reference components807. Sensor components 806 comprise an inductor and a modulatingelement, whereas reference components 807 comprise an inductor. Thestrain on the blade moves the modulating element in relation to theinductor in sensor components 806 (as discussed above in relation toFIGS. 5 a, 5 b, and 5 c) modulating wireless coupling 804. Wirelesscoupling 805 is not modulated by the strain on the blade, and may beused as a reference to determine any effects on coupling 804 due tonoise, temperature variation, or transmit power variations. The strainon the blade is then calculated based on couplings 804 and 805 at readerelectronics 808. As wireless coupling 805 is not affected by strain, butmay be modulated by variations in temperature or coupling strength,confounding effects of temperature and coupling strength may be removedfrom the strain data, and a corrected strain measurement is obtained,giving increased accuracy, sensitivity and specificity. Additionally,information about other variables in the rotary machinery, such as theoperating temperature, may be assessed independently of strain; thisknowledge may be used to determine the overall health of the rotarymachinery.

FIGS. 9 a and 9 b show further embodiments of a strain sensor comprisingauto-referencing. FIG. 9 a shows a capacitive approach. Receivingelement 901 a and reader electronics 904 a are disposed around thestationary component or approximately at the perimeter area of therotating components, or, for the example of an engine, the blades (notshown). Transmitting element 902 a, sensor components 905 a, referencecomponents 906 a, and switches 907 a and 908 a are disposed on therotating blade. Sensor components 905 a comprise a capacitor and a highpermittivity material, and reference components 906 a comprise acapacitor. Switches 907 a and 908 a may be used to complete the circuitwith transmitting component 902 a using either sensor components 905 aor reference components 906 a, allowing reader electronics 904 a toobtain readings of wireless coupling 903 a either with or without thepresence of the modulating element. Reader electronics 904 a maytherefore cancel out any effects on wireless coupling 903 a due tonoise. FIG. 9 b shows an inductive approach; in FIG. 9 b, sensorcomponents 905 b comprise an inductor and a high permeability material,and reference components 906 b comprises an inductor.

FIG. 10 shows an embodiment of a method 1000 of detecting strain in acomponent of a rotary machine. In block 1001, a first coil and a secondcoil are wirelessly coupled. In block 1002, the wireless coupling ismodulated by a modulating element located on the rotating component. Inblock 1003, the strain in the rotating component is calculated based onthe modulation of the wireless coupling.

In some embodiments, the modulating element may comprise a highpermeability material in an inductive embodiment of a wireless strainsensor, or a high permittivity material in a capacitive embodiment. Someexamples of high permeability materials that may be used in embodimentsof a wireless strain sensor include, but are not limited to, ironalloys, nickel alloys, an iron-nickel alloy, chrome, or otherferromagnetic alloys. Examples of high permittivity materials mayinclude, but are not limited to, oxides, ceramics, alumina, bariumsilicate, as well as conventional capacitor ceramic material such as NPOand X7R, or LiNbO₃. An appropriate material may be selected based on theoperating temperature of the rotary machine that is being measured forstrain, as different materials may have different magnetic responses asdifferent temperatures. Embodiments of a strain sensor may be used todetect strain in any machine that comprises rotating components,including but not limited to a compressor or a turbine in an aircraftengine, power generation turbines such as gas or steam turbines, or agenerator.

While the disclosure has been described with reference to exemplaryembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the disclosure. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the disclosure without departing fromthe essential scope thereof Therefore, it is intended that thedisclosure not be limited to the particular embodiment disclosed as thebest mode contemplated for carrying out this disclosure, but that thedisclosure will include all embodiments falling within the scope of theappended claims.

Also, the terms “first”, “second”, “bottom”, “top”, and the like do notdenote any order, quantity, or importance, but rather are used todistinguish one element from another; and the terms “the”, “a”, and “an”do not denote a limitation of quantity, but rather denote the presenceof at least one of the referenced items. The modifier “about” used inconnection with a quantity is inclusive of the stated value and has themeaning dictated by the context or includes at least the degree of errorassociated with measurement of the particular quantity. Furthermore, allranges reciting the same quantity or physical property are inclusive ofthe recited endpoints and independently combinable.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to make and use the invention. The patentable scope of the inventionis defined by the claims, and may include other examples that occur tothose skilled in the art. Such other examples are intended to be withinthe scope of the claims if they have structural elements that do notdiffer from the literal language of the claims, or if they includeequivalent structural elements with insubstantial differences from theliteral language of the claims.

1-10. (canceled)
 11. A method of detecting strain in a rotatingcomponent of a rotary machine, comprising: wirelessly coupling atransmitting element and a receiving element; modulating at least onecharacteristic of the coupling with a modulating element located on therotating component; and calculating the strain in the rotating componentbased on the modulation of the coupling.
 12. The method of claim 11,further comprising disposing the transmitting element and the receivingelement on a stationary component at a perimeter of the rotatingcomponent.
 13. The method of claim 11, further comprising disposing thereceiving element on a stationary component at a perimeter of therotating component, and placing the transmitting element on the rotatingcomponent.
 14. The method of claim 13, further comprising providing astrain sensor circuit on the rotating component, the strain sensorcircuit comprised of the transmitting element, the modulating element,and an inductor, wherein a distance between the modulating element andthe inductor varies with the strain on the rotating component.
 15. Themethod of claim 14, further comprising providing a reference circuit onthe rotating component, the reference circuit comprising a secondinductor, and comparing an output of the reference circuit to an outputof the strain sensor circuit to determine an effect of noise on thewireless coupling.
 16. The method of claim 13, further comprisingproviding a strain sensor circuit on the rotating component, the strainsensor circuit comprised of the transmitting element, the modulatingelement, and a capacitor, wherein a distance between the modulatingelement and the capacitor varies with the strain on the rotatingcomponent.
 17. The method of claim 16, further comprising providing areference circuit on the rotating component, the reference circuitcomprising a second capacitor, and comparing an output of the referencecircuit to an output of the strain sensor circuit to determine an effectof noise on the wireless coupling.
 18. The method of claim 11, whereinthe wireless coupling between the transmitting element and the receivingelement is a magnetic coupling.
 19. The method of claim 11, wherein therotary machine comprises a turbine engine, and wherein the rotatingcomponent comprises a blade.
 20. A strain sensing system, comprising: atransmitting element; a receiving element wirelessly coupled to thetransmitting element; a modulating element selected to modulate one ofan inductive element or a capacitive element and located on a rotatingcomponent of a rotary machine, wherein the modulating element modulatesthe one of an inductive element or a capacitive element and the wirelesscoupling between the transmitting element and the receiving element,wherein the modulation of the one of an inductive element or acapacitive element and the wireless coupling is indicative of strain onthe rotating component; and a processor configured to calculate thestrain in the rotating component based on the modulation of the wirelesscoupling.
 21. The method of claim 11, wherein the modulating element isformed of one of an inductive element or a capacitive element.
 22. Themethod of claim 11, wherein step of the modulating at least onecharacteristic of the coupling includes modulating at least one of areflection coefficient, an absorption coefficient, an s-matrixcoefficient, a resonance frequency or a quality factor.
 23. A strainsensor comprising: a transmitting element; a receiving elementwirelessly coupled to the transmitting element and defining a wirelesscoupling channel therebetween; and a modulating element disposed betweenthe transmitting element and the receiving element, wherein themodulating element modulates the wireless coupling channel subsequent totransmission by the transmitting element and prior to receipt by thereceiving element, wherein the modulation is indicative of strain on therotating component.
 24. The strain sensor of claim 23, wherein thetransmitting element and the receiving element are located on astationary component at a perimeter of the rotating component.
 25. Thestrain sensor of claim 23, wherein the modulating element is located onthe rotating component.
 26. The strain sensor of claim 23, wherein thewireless coupling between the transmitting element and the receivingelement is a magnetic coupling.